1. Field of the Invention
This invention relates to a matrix plate for electrophotographic platemaking, a production thereof and a printing plate obtained by exposing to radiation and developing the matrix plate. More particularly, it relates to a plate-making matrix plate sensitive to a semiconductor laser and capable of directly making a plate by the electrophotographic process, a production thereof and a printing plate obtained by exposing to radiation and developing the matrix plate.
2. Description of the Prior Art
The technological advances in computer image processing and mass storage communication have recently encouraged proposal as a new system of the so-called phototelegraphic printing to be effected by processing a given image with a computer thereby obtaining image information in the form of a digital signal, electrically transmitting the image information with a telephone circuit or a communications . satellite, subjecting the image information reaching the receiver to the operation of a scanner device on the receiver's side, and irradiating this image information with a laser in the scanning manner.
The conventional matrix plate for platemaking has relied predominantly on the method using photosensitive resin (PS plate method). In the case of the PS plate method, since the platemaking is accomplished by causing the received information to be written in a silver salt film as a provisional step, pressing the film fast against a matrix plate, and exposing the film to radiation, this method has a disadvantage that the plate-making operation necessitates a voluminous apparatus and consumes much time. Further, most photosensitive materials for the PS plate method make use of a photochemical reaction and, therefore, require ample exposure to radiation and generally are deficient in sensitivity. Thus, the photosensitive materials of the PS plate method have a disadvantage that they are incapable of producing fully satisfactory image information by the exposure to a low-output inexpensive semiconductor laser.
For the solution of the problems of the PS plate method described above, a method which uses a silver halide photosensitive material for photo-making matrix plate and a method which utilizes the electrophotographic process have been proposed and partly put to practical use. Though the former method enjoys highly satisfactory sensitivity, it suffers from a disadvantage that the plate is deficient in resistance to the impact of printing and is unduly expensive. In contrast, the latter method allows direct platemaking, enjoys relatively high sensitivity and inexpensiveness, and promises successful production of a printing plate highly resistant to the impact of printing. Thus, it has been the subject of active study in recent years.
In the matrix plate for electrophotographic platemaking, zinc oxide and organic compounds have been used as photoelectroconductive substances. The plate-making matrix plate using zinc oxide generally suffers from disadvantages such as (A) the fact that the produced printing plate tends to be defiled because the non-image part thereof is deficient in hydrophilicity, (B) the fact that the produced printing plate is deficient in resistance to the impact of printing because it suffers the photosensitive layer to peel off under the mechanical pressure exerted thereon during the course of printing or owing to the permeation therein of the dampening water, and (C) the fact that the produced printing plate, in spite of sensitization with pigment performed in advance thereon for impartation of sensitivity to the region of visible light, exhibits no fully satisfactory sensitivity in the region of long wavelength exceeding 600 nm and allows no easy effective exposure with a semiconductor laser.
In the case of the plate-making matrix plate using an organic photoelectroconductive compound, the platemaking is accomplished by dispersing the organic photoelectroconductive compound in a binder resin formed mainly of an alkali-soluble resin thereby preparing a photosensitive material, applying the photosensitive material to an abraded surface of a substrate such as of aluminum sheet thereby superposing a photosensitive layer on the substrate, forming a toner image by the electrophotographic technique on the photosensitive layer, and dissolving and removing the non-image part with an alkali extractant.
Numerous electrophotographic plate-making matrix-plates have been proposed which are provided with a photosensitive layer having a varying organic photoelectroconductive compound dispersed in an alkali-soluble resin. For example, JP-A-54-134,632(1979), JP-A-55-105,254(1980), and JP-A-55-153,948(1980) disclose such matrix plates using phenol resin as the alkali-soluble resin. When a phenol resin is used as a binder resin for such a photoelectroconductive organic compound, however, the produced film has a disadvantage that it is brittle and, therefore, deficient in resistance to the impact of printing.
JP-A-58-76,843(1983), JP-A-59-147,355(1984), JP-A-60-17,752(1985), JP-A-60-243,670 (1985), US-A-4,868,079(1989), and JP-A-64-23,260(1989) disclose matrix plates using a styrene-maleic acid copolymer as the alkali-soluble resin. When a styrene-maleic acid copolymer is used as a binder resin for an organic photoelectroconductive compound, however, there arises a disadvantage that the produced film is so hard that the printing plate tends to sustain cracks when it is bent. Acrylic resins have been employed in many cases. JP-A-54-89,801(1979) discloses a matrix plate using an aqueous acrylic resin as a binder resin and an e type crystalline copper phthalocyanine as an organic photoelectroconductive compound. These matrix plates are capable of forming an image by the electrophotographic process. They, however, suffer from a disadvantage that they are not easily etched with an aqueous alkali solution and are incapable of effective exposure to a radiation in the near infrared region such as a semiconductor laser.
JP-A-56-146,145(1981) discloses a method which uses as a binder resin such an acrylic resin as an acrylic acid/methyl methacrylate/butyl acrylate copolymer, for example, and as organic photoelectroconductive compounds a condensed polycyclic quinone type pigment and an oxadiazole derivative. Though the matrix plate obtained by this method allows an etching treatment to be effected easily with an aqueous alkali solution, it has a disadvantage that it possesses no fully satisfactory electrophotographic properties and betrays poor stability to withstand storage for an extended period. It also has a disadvantage that it is incapable of effective exposure to radiation in the near infrared region such as a semiconductor laser. It has a problem of inferior resistance to the impact of printing because it is incapable of effective exposure to radiation in the near infrared region such as a semiconductor laser or, if it is adapted somehow or other to attain the exposure, it exhibits no fully satisfactory behavior as in the electrophotographic properties.
An object of this invention, therefore, is to provide a novel matrix plate for electrophotographic platemaking, a production thereof and a printing plate produced by exposing to radiation and developing this matrix plate.
Another object of this invention is to provide an electrophotographic plate-making quality matrix plate resorting to an improved method using an organic photoelectroconductive compound, a production thereof and a lithographic printing plate.
A further object of this invention is to provide an electrophotographic plate-making quality matrix plate excelling in electrophotographic properties and alkali-extractability, a production thereof and a lithographic printing plate excelling in printing properties.
Still another object of this invention is to provide an electrophotographic plate-making quality matrix plate capable of producing a printing plate excelling in stability to withstand storage for an extended period and resistance to the impact of printing.
Yet another object of this invention is to provide an electrophotographic plate-making quality matrix plate which is furnished with a photosensitive layer excelling in lightfastness and weatherability owing to the use of a binder resin possessing highly satisfactory fast adhesiveness to a substrate and satisfactory mechanical strength.
A further object of this invention is to provide an electrophotographic plate-making quality matrix plate exhibiting high sensitivity even in the region of near infrared wavelength and allowing effective exposure to a semiconductor laser.